Leptin concentrations in serum from a randomly recruited sample of 50- to 80-year-old men and women: positive association with plasma insulin-like growth factors (IGFs) and IGF-binding protein-3 in lean, but not in obese, individuals.
OBJECTIVE
The GH/IGF axis is thought to play an important role in the regulation of body composition throughout life. Changes in body fat stores also affect the activity of the GH/IGF axis, but the mechanisms whereby body fat status is signaled to the GH/IGF axis are poorly understood. The newly discovered protein leptin is exclusively produced by adipocytes, and circulating concentrations of leptin closely reflect body fat stores.


METHODS
We here examined whether leptin might be associated with the activity of the GH/IGF axis in a population-based sample.


METHODS
Circulating concentrations of leptin, IGF-I, IGF-II, and insulin-like growth factor-binding protein-3 (IGFBP-3) were measured in a population-based sample of 50- to 80-year-old men (n=217) and women (n=198) by specific RIA.


RESULTS
All three IGF components were significantly positively correlated with leptin in lean women (body mass index (BMI) <25 kg/m2). IGF-II was also positively correlated with leptin in lean men, and positive correlation of leptin with IGF-I in lean men was of borderline statistical significance. In contrast, no correlation was observed in moderately overweight (BMI 25-30kg/m2) and obese individuals (BMI >30 kg/m2).


CONCLUSIONS
Our study shows that serum leptin concentrations are significantly associated with circulating IGF components in lean elderly subjects. The precise mechanism of this interaction between leptin and the GH/IGF system remains to be determined.
Seck
T
T
Department of Internal Medicine I, University of Heidelberg, Germany.
Englaro
P
P
Blum
W F
WF
Scheidt-Nave
C
C
Rascher
W
W
Ziegler
R
R
Pfeilschifter
J
J
D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D005260:Female; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood*; D020738:Leptin; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood* / Q000473:pathology; D009994:Osmolar Concentration; D011506:Proteins / Q000032:analysis*; D012016:Reference Values; D013002:Somatomedins / Q000032:analysis*
D018972:Insulin-Like Growth Factor Binding Protein 3; D020738:Leptin; D011506:Proteins; D013002:Somatomedins